The invention concerns an apparatus for grinding and lapping sealing surfaces in slide valves and the like in situ or in the workshop, with a base plate which can be attached to the housing of a slide valve or the like, a drive, and a rotatably mounted tool plate which is connected to the drive by a supporting element and coupled to it by a transmission element, the supporting element being supported releasably and with adjustable height on the base plate by means of a guide piece which is pivotably about a pivot shaft extending perpendicularly to the longitudinal axis of the supporting element and essentially perpendicularly to the axis of the tool plate, wherein rigidly connected to the guide piece is one end of a rocker which extends perpendicularly to the pivot shaft and whose other end is coupled to a correcting element which is supported adjustably on the base plate and allows adjustment of the contact pressure of the tool plate in the direction of the surface to be machined.
Apparatuses of this kind are used in particular to grind and lap sealing surfaces in valves, slide valves, valve discs, valve wedges, valve plates, flanges, pump housings, etc., while they are in the fitted position. In this way, wear phenomena and deposits on these surfaces are eliminated without the workpieces concerned having to be taken out of the respective equipment, and hence without this equipment having to be dismantled.
It has proved extremely difficult, and even impossible with many known apparatuses, to achieve the desired planeness of the surface to be machined with known apparatuses of this kind. This is due to the fact that the pressure acting in an axial direction on the tool plate loads to deformation of this plate, and/or that machining elements mounted on this tool plate, e.g. grinding heads, undergo undesirable tilting according to the contact pressure which arises, on account of elastic deformation and the bearing play which is always present to a greater or lesser degree. If in this case the machining elements are supported on the tool plate by means of arms, attempts have been made, by using feeler gauge strip, to compensate for the inevitably occurring tilt of the working surfaces of the machining elements. But this procedure is very time-consuming, and requires specially qualified skilled workers.